基于变异系数TOPSIS法的土地利用效益测度研究——以武汉城市圈为例

从社会效益、经济效益、生态效益和环境效益四方面,构建土地利用效益评价体系,采用变异系数TOPSIS法和耦合协调度模型,对武汉城市圈土地利用效益和耦合协调度进行实证分析。结果显示:(1)武汉城市圈土地利用效益具有两级分化明显区域差异悬殊的特征。社会经济效益以其他城市的低级效益为主,武汉的优良效益为辅,生态环境效益以其他城市的良好效益为主,鄂州的低级效益为辅,而综合效益则以其他城市的中度效益为主,鄂州的低级效益和武汉的优良效益为辅;(2)武汉城市圈土地利用效益耦合度均处于拮抗阶段,且区域差异较小;(3)武汉城市圈土地利用效益耦合协调度区域差异较显著,包括中度协调耦合和高度协调耦合两种类型。武汉处于高度协调耦合阶段,其他城市处于中度协调耦合阶段。     

城市土地利用综合效益耦合分析——以武汉市为例

实现社会经济效益和生态环境效益的均衡发展,是全面协调可持续发展的必然要求。在深入分析土地利用效益评价等有关理论的基础上,结合武汉市土地利用现状,从土地产出的综合效益均衡角度,形成了由社会经济效益和生态环境效益两个子系统构成的评价指标体系,采用主成分分析法确定各指标权重,对武汉市土地利用社会经济效益和生态环境效益进行评价;再构建武汉市土地利用的社会经济效益与生态环境效益的耦合模型,辨识两者之间的协调关系,分析两者之间的协调程度。研究结果显示,1996—2010年武汉市土地利用社会经济效益与生态环境效益均呈上升态势,其中社会经济效益表现出起点低、增幅大、速度快的特征,而生态环境效益则呈现出起点较高,增幅较大,在波动中稳定上升的特点。土地利用社会经济和生态环境效益耦合度评价结果显示,在1996—2010年,武汉市城市土地利用社会经济效益与生态环境效益的耦合演化进程近似于对数曲线,从形成初期的不协调至激烈博弈后的利益分化,之后经历相对最佳协调后,又逐渐向不协调发展并呈现新的演化特点。     

哈尔滨市土地利用效益耦合关系研究

定量研究城市土地利用效益之间的耦合规律,是建立有效协调机制的关键,为城市土地利用总体规划的制订和城市的可持续发展提供重要依据。土地利用效益包括土地利用社会经济效益与生态环境效益,以哈尔滨市域为研究区,运用多指标综合评价法计算2000—2009年哈尔滨市土地利用社会经济效益与生态环境效益综合值,基于系统理论建立了二者之间的耦合模型,用耦合度来表达这两种效益之间的协调程度。结果表明:哈尔滨市土地利用效益的耦合度演化分为3个阶段,2000—2002年,土地利用效益耦合度从-30.62°快速增长到67.28°,从低级共生到协调发展,2002—2005年,耦合度从67.28°上升到85.14°,即从最佳协调状态向不甚协调状态发展。2005—2009年,耦合度为85.14°～86.85°,土地利用效益的协调程度有所下降。     

城市土地集约利用综合效益演化研究——以湖北省咸宁市为例

开展城市土地利用效益评价有助于衡量城市土地集约利用水平,实现城市土地的高效协调利用.从社会效益、经济效益、生态效益和环境效益4个方面,构建了城市土地集约利用效益评价体系,采用熵值法确定了指标权重,对咸宁市1999-2008年的城市土地集约利用效益及协调度进行了综合评价.结果表明:(1)咸宁市城市土地集约利用社会效益、经济效益和生态效益明显增加,环境效益快速下降,综合效益稳步上升.(2)城市土地集约利用效益协调度除最初两年处于极不协调和不协调状态外,其他时间均处于基本协调或比较协调状态.鉴于此,提出了加大产业结构调整、提高城市土地集约利用程度和加强生态环境保护等相应的对策建议.     

京津冀地区城市土地集约利用与城镇化耦合协调关系研究

以京津冀地区作为研究区域,建立城市土地集约利用指标体系与城镇化指标体系,采用均方差权值法,并建立耦合协调模型,计算2011年13个地级以上城市的土地集约利用和城镇化指数及二者的耦合度和协调发展度。按照耦合协调度的高低将13个城市划分为4大类;每个大类内部再按照城市土地集约利用与城镇化指数的关系,分为城市土地集约利用滞后和城镇化滞后的2个亚类。结果表明:京津冀地区城市土地集约利用和城镇化之间关系密切,二者相互作用,但并非同步发展;城市土地集约利用程度与城镇化耦合程度基本上处于颉颃阶段,耦合协调度水平总体不高,区域差异明显。     

云南城市生态环境与农村生态环境耦合协调关系分析

利用2009~2013年相关数据,在城市生态环境与农村生态环境耦合协调关系评价指标体系构建的基础上,运用熵权法确定指标权重,同时引入耦合度与耦合协调度模型,定量计算云南城市生态环境与农村生态环境的耦合度与耦合协调度,并结合耦合度阶段与协调度类型划分标准对两者间的耦合协调关系进行定量评价。研究表明:从综合指数看,云南城市生态环境综合指数波动较大,农村生态环境综合指数变化比较平稳,且城市生态环境综合指数增幅小于农村生态环境综合指数增幅;从耦合度看,云南出现由农村生态环境滞后向城市生态环境滞后的转变,城市生态环境与农村生态环境耦合度经历了从磨合阶段到高水平耦合阶段的变化,两系统间的发展方向越趋有序,关系越趋稳定;从协调度看,云南城市生态环境与农村生态环境协调度呈上升趋势,耦合协调类型从低度协调转变为中度协调并最终呈现良好协调的发展态势。     

宁夏回族自治区生态环境与经济发展耦合协调研究

为了研究区域生态环境与社会经济协调发展状况,以宁夏回族自治区为例,通过构建评价指标体系,综合运用熵权法、耦合协调度模型、剪刀差方法以及耦合度模型对宁夏生态环境与社会经济发展状况、耦合协调水平以及耦合度演化趋势进行了综合分析。结果显示:研究期间宁夏生态环境系统综合发展指数呈波动上升的变化趋势,社会经济发展水平逐年上升;耦合协调指数由0.3225上升至0.5962,说明区域生态环境与社会经济的关系不断缓和,趋向于协调发展;剪刀差呈先减后增的“U”型变化趋势,说明两系统发展差异呈先减小后增大的变化态势;宁夏生态环境与社会经济发展耦合度介于(45°,90°],说明两系统处于协调发展阶段,而耦合度整体呈上升态势,说明经济发展与生态环境之间的矛盾开始显现。基于耦合模型所建立的耦合协调度,较好地反映了宁夏生态环境与社会经济之间交互胁迫的耦合发展过程,对于正确认识宁夏生态与经济系统耦合发展规律,促进宁夏生态与经济协调发展具有重大意义。     

甘肃省庆阳市土地集约利用与土地利用结构的耦合协调关系

[目的]探究甘肃省庆阳市土地集约利用与土地利用结构之间的协调关系,为该市土地利用结构优化和社会经济的可持续发展提供理论依据。[方法]以庆阳市为例,采用多因素综合评价法计算2007—2016年土地集约利用、土地利用结构的综合指数,应用耦合协调模型,分析二者变化特征及耦合协调关系。[结果]①庆阳市土地集约利用综合指数呈上升趋势,达到了高度集约利用水平。②庆阳市土地利用结构信息熵总体呈下降趋势,均衡度逐渐降低,优势度逐渐增强。③土地集约利用与土地利用结构耦合度呈先上升后下降的趋势,耦合协调度都呈上升趋势,二者耦合性越来越强,相对呈现出协调、稳定的发展趋势。[结论] 2007—2016年庆阳市土地集约水平总体变化呈逐年上升状态,但信息熵呈下降趋势,是由于大力开发未利用地,植树造林使得土地利用结构调整。土地集约利用和土地利用结构两系统协调度都呈上升趋势,二者耦合性越来越强。说明庆阳市在大力推动经济发展的同时,也注重提高土地利用的效率,调整土地利用结构,优化布局。     

城市土地集约利用与城市化效率的时空耦合关系——以辽中南城市群为例

基于耦合理论运用模糊层次分析法和DEA方法对辽中南城市群1987—2012年城市土地利用集约度和城市化效率进行测算,然后采用耦合度和耦合效应指数进行二者耦合阶段、耦合效应的时空分析。结果表明:(1)研究期内辽中南城市群城市土地利用处于基本集约阶段,城市化效率呈波动上升态势,城市土地集约利用和城市化效率的耦合度变化曲线为浅口"U"型。(2)辽中南城市群处于弱耦合到强耦合的转化阶段。西强东弱的耦合度分布正转化为以东西方向为轴,南北对称分布的格局。表现为以沈阳、大连为高值双核心,沈大联系带上辽阳、鞍山、营口、盘锦为次高值分布,东部为低值区域。(3)耦合效应的变化趋势为从负效应到正效应的过程,城市耦合效应长期存在东、西差异。2012年城市群耦合效应出现"质"的变化,全局协调性得到优化。(4)大连的耦合阶段与耦合效应协调同步,耦合作用促进城市发展;沈阳、鞍山、盘锦耦合效益超前于耦合阶段,应适当控制城市化步伐,缓解用地压力,提高社会效益;其余城市大体处在较低耦合阶段,耦合效应没有带来积极的发展红利。     

河北省城市土地集约利用与城市化的耦合协调度分析

基于城市土地集约利用与城市化的耦合协调特征,构建耦合协调度模型和相对发展度评价模型,对河北省11个市2001-2010年的耦合协调发展度和相对发展度进行了测算分析.结果表明:从耦合协调度的时序特征来看,系统逐渐从颉颃期、磨合期向协调期发展,城市土地集约利用与城市化趋于同步发展;从空间特征来看,耦合协调度呈现出片状分区集聚的特征,东部沿海城市耦合协调水平较高,北部地区耦合协调水平较低,中部地区发展平稳.随着时间的推进耦合协调关系逐渐优化.     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.     

Short-term variation in the concentration of selected ions within individual tropical rainstorms

Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl^–, NO₃ ^– and SO₄ ^2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.     

The 5S rRNA gene diversity in the genus <Emphasis Type="Italic">Secale</Emphasis> and determination of its closest haplomes

We analyzed 127 rDNA sequences (5S DNA units) obtained from 23 seed accession samples from more or less 10 taxa in wild and cultivated rye, genus Secale L. The sequences fell into two known groups, here assigned to two unit classes, viz. long R1 and short R1 (designations to reflect on R haplome of rye). The different taxa could not be fully differentiated based on the 5S DNA units. We searched for 5S DNA sequences from known unit classes most closely similar to the long R1 and the short R1. One set with the long R1 unit class contained sequences of the long P1 unit class from Agropyron (P haplome) and from Kengyilia (StYP haplome), long J1 from Thinopyrum (J haplome), whereas the set with the short R1 included the long S1 from Pseudoroegneria (St haplome) and Kengyilia (StYP haplome), the short J1 from Thinopyrum (J haplome) and the short V1 from Dasypyrum (V haplome). Each of the two sets was analyzed separately by maximum likelihood (ML) phylogenetic analysis from which we were able to infer that the 5S DNA units of Secale differentiated in a non-clock fashion and followed the HKY substitution model in the gene tree with the long R1 unit class and the HKY + G in the gene tree with the short R1 unit class. A complementary Bayesian analysis yielded identical tree topologies to the ML ones for each of the two sequence sets. In the tree with the long R1 units the long P1 and long J1 unit classes were closest to the long R1 unit class, whereas in the tree with the short R1 units the long S1 and short J1 unit classes were closest to the short R1 unit class, indicating possibly a close relationship between the St, J and R haplomes.     

Leaf litter selection by detritivore and geophagous earthworms

Summary Litterbag experiments with 10 different kinds of leaf litter showed that detritivore (Lumbricus species) and geophagous (Aporrectodea species) earthworms prefer certain litter types over others, since different numbers of worms were found below the litter after 50–52 days of exposure in a pasture. The detritivores preferred Fraxinus, Tilia, and predecomposed Ulmus and Fagus litter to Fagus litter and paper, while geophages preferred Tilia litter to Alnus and Ulmus litter, so that the two groups of earthworms showed different preferences. The detritivores seemed to be more selective than the geophages. The palatability of the litter was examined in relation to the C: N ratio, the lignin concentration and the initial and final polyphenol concentration. The numbers of detritivores were significantly correlated with the C: N ratio and the final polyphenol concentration, so that selection of litter seems to be related to palatability. The numbers of geophages were not significantly correlated with any of the parameters for palatability. The disappearance of litter after 50–52 days appeared to be due to detritivore activity, since the numbers found below the litter were positively and significantly correlated with the litter disappearance. There was no significant correlation with geophage activity. This indicates that detritivores use litter as food, and therefore influence the composition of the litter layer.     

Nematode succession and microfauna-microorganism interactions during root residue decomposition

The quality of plant material affects the vigor of the decomposition process and composition of the decomposer biota. Root residues from hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and vetch+rye, packed in litterbags were placed in pots of soil at 15 C and the content of the bags was analyzed after 2, 4, 8 and 12 weeks. Bacterial biomass did not differ between residues with contrasting composition. Among bacterivores groups of nematodes that require high bacterial production dominated in fast decomposing resources whereas flagellates with smaller requirements prevail in slower decomposing resources. Biomass of bacterial feeding nematodes correlated positively with early phase (0-2 wk) decomposition that increased in the order: rye< vetch+rye<vetch. Bacterial biomass therefore seems to be under top-down (predation) control during early decomposition. In contrast, the fungal biomass differed between resources with highest values for rye. Moreover, this increase in fungal biomass occurred later during succession and was correlated with decomposition activity for rye in that period. Fungal biomass therefore seems to be under bottom-up (resource) control. The composition of the nematode assemblages (composed of 25 taxa) showed a clear relationship to initial plant resource quality as well as decomposition phase. Early successional microbivorous nematodes vary according to resource quality with demanding bacterivores+predators (Neodiplogasteridae) dominating in vetch and less demanding bacterivores (Rhabditidae) and fungivores (Aphelenchus) being equally common in vetch and rye. Later in the succession (2-4 wk) bacterivorous Cephalobidae and fungivorous Aphelenchoides prevailed similarly on the different root materials whereas bacterivorous protozoa and the amoebal fraction thereof dominated in rye. At week 12 no species dominated the nematode assemblages that were similar between the resources. The differences between nematode assemblages among plant resources at 2 week were similar to the results of a field study sampled after 6 weeks with the same soil and plant resources. This lends support to the relevance of the successional patterns observed in this incubation study.     

Cycling of extracellular DNA in the soil environment

Upon entering the soil environment, extracellular DNA is subjected to dynamic biological, physical, and chemical factors that determine its fate. This review concerns the fate of both recombinant and non-recombinant sources of DNA. A schematic of DNA cycling coupled with genetic transformation is presented to understand its behavior in soil. Extracellular DNA may persist through cation bridging onto soil minerals and humic substances, be enzymatically degraded and restricted by DNases of microbial origin, and/or enter the microbial DNA cycle through natural transformation of competent bacteria. Lateral gene transfer may disseminate DNA through the microbial community. An understanding of DNA cycling is fundamental to elucidating the fate of extracellular DNA in the soil environment.